Hello 'littlelouienwt',
Did you not receive the adjusted invoice in your regular email?
No matter, - if the seller has indeed sent it, you don't actually need the invoice itself because
the changes (the adjusted shipping charges) will be reflected at the checkout when you go to
pay for the item from your Purchase History page on ebay.
Just find the listing and click Pay now on the right side. If you do not see the new shipping
service and appropriate charges available (some sellers change it and you only see the new
option, and some sellers add it on and now you would have a choice), contact the seller
and explain what it is that you do see.
Even sellers make mistakes, -- although not very often, they'll tell you. 